Abstract
BackgroundPlant-based mosquito control methods may use as a supplementary malaria vector control strategy. This study aimed to evaluate the effect of smoking ethno-medicinal plants on indoor density and feeding activity of malaria vectors at early hours of the night and its residual effect after midnight in southern Ethiopia.MethodsBoth field and tent trials were conducted to evaluate the impact of smoking Juniperus procera leaves, Eucalyptus globulus seeds and Olea europaea leaves in Kolla Shara Village from July 2016 to February 2017. For the field trial, five grass-thatched traditional huts (three for ethno-medicinal plants and two as control [only charcoal smoking and non-charcoal smoking]) were used. Indoor host-seeking mosquitoes were collected by CDC light traps. A Latin square design was employed to minimize the bias due to the variation in house location and different sampling nights. For the tent experiment, 25 3–5-day-old starved wild female Anopheles mosquitoes reared from the larvae were released into the tents where a calf was tethered at the mid-point of each tent.ResultsA total of 614 Anopheles mosquitoes belonging to 5 species were collected from 5 huts, of which 93.4% was An. arabiensis; O. europaea, E. globulus and J. procera reduced the indoor density of An. arabiensis, with the mean percentage drop of 80%, 73% and 70%, respectively. In the tent trial, smoking of these plants had significant knockdown effects and inhibited feeding on the calves (F = 383.5, DF = 3, P < 0.01). The mean knockdown effect due to O. europaea was relatively high (17.7 ± 0.54; 95% CI 16.8–18.6), while it was only 0.9 ± 0.1 (95% CI 0.29–1.52) in the control tents. All the test plants used in the tent trial caused significantly inhibited feeding activity of An. arabiensis on the host (F = 383.5, DF = 3, P < 0.01). About 94.5%, 89.5% and 86% of mosquitoes were unfed because of the smoking effect of O. europaea, E. globulus and J. procera, respectively, whereas only 19.5% were unfed in the control tent.ConclusionsSmoking ethno-medicinal plant materials reduced indoor density of malaria vectors and inhibited feeding on calves inside the tents. Thus, plant-based mosquito control methods may play a vital role in reducing mosquito bites in the early hours of the night and thereby reduce residual malaria transmission.Graphical
Highlights
Plant-based mosquito control methods may use as a supplementary malaria vector control strategy
Anopheles species composition A total of 614 adult female Anopheles mosquitoes belonging to five species, Anopheles arabiensis, An. demeilloni, An. funestus group, An. pretoriensis and An. pharoensis, were collected from five huts selected for the field experiment trial
Effect of smoke on indoor density of mosquitoes during smoking hours Smoking O. europaea, E. globulus and J. procera had a significant effect on the indoor density of host-seeking malaria vectors (F = 43.3, DF = 4; P < 0.001)
Summary
Plant-based mosquito control methods may use as a supplementary malaria vector control strategy. The changing behavior of the vectors, such as early hours and outdoor biting, as well as resting, could maintain malaria transmission even in areas with maximum coverage of the existing tools [6]. This shifting in resting and feeding behaviors in the main malaria vectors in response to control methods might have a negative impact on the current indoor-based malaria vector control interventions [7, 8]. The principal malaria vector, Anopheles arabiensis, in the northern and south-central parts of Ethiopia shows exophilic behavior that might challenge IRS-based malaria control interventions. An. arabiensis has developed resistance to most public health insecticides, which has increased interest in searching for new insecticides and alternative vector control approaches [9, 10]
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